An automated 'bio-intact' PTH assay: a step towards standardisation and improved correlation with parathyroid function in renal disease

BACKGROUND: Most methods for the determination of parathyroid hormone (PTH) show cross-reactivity with N-truncated forms of PTH. The analytic and diagnostic value of a recently developed automated PTH test without this cross-reactivity was examined. METHODS: The PTH levels of 73 patients undergoing hemodialysis were compared using the 'bio-intact' PTH (Nichols Institute Diagnostics) and 3 'intact' PTH tests (from Nichols, Roche Elecsys and Diagnostics Corporation DPC). Further, the (non 1-84) PTH fragment and the PTH ratio (bio-intact PTH/(non 1-84) PTH) were calculated. All results were then correlated with biochemical bone markers (bone-specific alkaline phosphatase and bone collagen C-terminal telopeptides in serum). RESULTS: 'Bio-intact' PTH values were lower than the PTH results generated by the 'intact' PTH assays. Results of all PTH tests were closely correlated (r=0.96-0.98, p<0.01). Correlations with biochemical bone markers were high (r=0.31-0.63, p<0.01), but no significant association between the PTH ratio and all other tests (r=-0.2 to 0.03) was found. CONCLUSIONS: In stable hemodialysis patients, the different PTH tests show a similar correlation with the bone markers. It is however desirable to measure PTH with assays devoid of any cross-reaction for a better comparability. In this study, the PTH ratio was not correlated with biochemical bone markers; the use of this ratio requires further investigation.     

Assay-specific decision limits for two new automated parathyroid hormone and 25-hydroxyvitamin D assays

BACKGROUND: The recent development of nonradioactive automated assays for serum parathyroid hormone (PTH) and 25-hydroxyvitamin D (25OHD) has made measurement of these two hormones possible in many laboratories. In this study, we compared two new assays for PTH and 25OHD adapted on an automated analyzer, the LIAISON, with two manual immunoassays used worldwide. METHODS: We studied 228 osteoporotic patients, 927 healthy individuals, 38 patients with primary hyperparathyroidism, and 167 hemodialyzed patients. Serum PTH was measured with the Allegro and the LIAISON assays, and 25OHD was measured with DiaSorin RIA and the LIAISON assay. Regression analysis was used to calculate decision thresholds for the LIAISON assays that were equivalent to those of the Allegro PTH and DiaSorin 25OHD assays. RESULTS: The 25OHD concentrations obtained with the LIAISON assay and the RIA in osteoporotic patients were well correlated (r = 0.83; P <0.001). Regression and Bland-Altman analyses suggested that the LIAISON 25OHD assay reads lower than the DiaSorin RIA at low concentrations but higher at high concentrations. However, the cutoff (50 nmol/L) used in our laboratories to define vitamin D insufficiency with the DiaSorin RIA is applicable to the LIAISON 25OHD assay. In 927 healthy individuals, the 3rd-97th percentile intervals were 3-80 ng/L and 13-151 nmol/L for the LIAISON PTH and 25OHD concentrations, respectively. However, 506 individuals (54.6%) were vitamin D-insufficient; we therefore considered only the 421 individuals with a LIAISON 25OHD >50 nmol/L as eligible for the reference population for the LIAISON PTH assay. In this group, the 3rd-97th percentile interval for LIAISON PTH was 3-51 ng/L. Considering upper reference limits of 46 and 51 ng/L for the Allegro and LIAISON assays, respectively, the frequency of above-normal PTH concentrations in patients with primary hyperparathyroidism was similar in both assays. Regression analysis between serum PTH measured by the Allegro and LIAISON assays in 167 hemodialyzed patients and the corresponding Bland-Altman analysis of these data suggest that the LIAISON PTH assay tends to read higher than the Allegro assay at low concentrations but lower at high concentrations (>300 ng/L). CONCLUSIONS: Because clinical decision limits for both PTH and 25OHD should be assay specific, we propose equivalences between these assays and two manual assays used worldwide. These assay-specific decision limits should help potential users of the LIAISON PTH and 25OHD assays.     

Intact parathyrin in postmenopausal women

To establish a reference range, we measured intact parathyrin (parathyroid hormone, PTH) in 245 healthy postmenopausal women, ages 42-75 years, with use of the Allegro Intact PTH Kit from Nichols Institute Diagnostics. We also assayed serum from a subset of 120 of the women with kits specific for mid-molecule PTH. The mean intact PTH concentration for the 245 women was 32 ng/L (95% confidence interval 14-60 ng/L). Intact PTH values in these subjects were not normally distributed, although calcium concentrations in the same samples were. There was positive, but not significant (r = 0.12, P = 0.06), correlation between intact PTH and age, and a significant negative correlation between serum calcium and intact PTH that was not observed between calcium and mid-molecule PTH. The improved sensitivity of the intact PTH assay makes it useful in studies of calcium homeostasis in the normal population.     

Multicenter evaluation of a rapid electrochemiluminescent adrenocorticotropic hormone (ACTH) immunoassay

BACKGROUND: Measuring plasma adrenocorticotropic hormone (ACTH) is a key step in the differential diagnosis of hypothalamic-pituitary-adrenal disorders. METHODS: The recently developed electrochemiluminescence Elecsys ACTH immunoassay (Roche Diagnostics, Mannheim, Germany) was evaluated at six clinical laboratories on the Modular E170 and/or the Elecsys 2010 (Roche Diagnostics) immunoanalysers. RESULTS: The within-run and between-run imprecision was 相似文献   

Immunoradiometric assay of parathyrin with polyclonal and monoclonal region-specific antibodies.

In this immunoradiometric assay (IRMA) of parathyrin (PTH) a polyclonal anti-amino-PTH(1-34) is the capture antibody and a radiolabeled monoclonal anti-hPTH(44-68) is the second antibody. Gel filtration of serum from a hyperparathyroid patient yielded only a single peak of PTH, corresponding to the elution position of synthetic PTH(1-84). Healthy elderly individuals (ages 78 +/- 5 y, mean +/- SD, n = 45) had PTH concentrations (21 +/- 13 ng/L) not significantly higher than those from healthy younger (38 +/- 11 y) adults (20 +/- 8 ng/L, n = 94). Assay results agreed well with those obtained with a carboxyl-terminal PTH assay both in normal subjects (r = 0.63, P less than 0.001) and in patients with primary hyperparathyroidism (r = 0.59, P less than 0.001). Both assays equally discriminated patients with surgically confirmed primary hyperparathyroidism from normal individuals, but the PTH(1-84) IRMA also allowed a nearly absolute discrimination between normal subjects and patients with primary hypoparathyroidism (undetectable serum PTH in 18 of 21 cases) and secondary hypoparathyroidism (caused by hypercalcemia that was caused by a malignant tumor, PTH 1.3 +/- 1.3 ng/L, n = 32). Moreover, the PTH(1-84) IRMA is more sensitive (detection limit in serum, 0.8 ng/L) and easier and quicker to perform than the carboxyl-terminal assay.     

Intraoperative parathyroid hormone analysis: A study of 200 consecutive cases

BACKGROUND: Immunoassays for parathyroid hormone (PTH), with short incubation times and results available in <15 min, have allowed intraoperative monitoring of the success of parathyroid surgery. The purpose of this study was to evaluate the analytical performance of a rapid PTH assay and its clinical performance in a series of 200 patients. METHODS: PTH was measured with a modified immunochemiluminometric assay with a 7-min incubation time (QuiCk-IntraOperative(TM) Intact PTH assay). The rapid assay was compared with results in a central laboratory (immunoradiometric assay) in 44 EDTA-plasma specimens. The rapid assay was used intraoperatively in 200 consecutive cases with specimens analyzed before and 5-10 min after resection of the hypersecreting parathyroid gland(s). RESULTS: Intraassay imprecision was 12% at 28 ng/L and 11% at 278 ng/L. Regression analysis of results of the rapid PTH assay and the IRMA PTH assay in 44 parathyroidectomy patients yielded y = 1.26x - 12 ng/L, S:(y|x) = 26.3 ng/L, r = 0.984, and in 40 of 44 patients with values <200 ng/L, y = 1.02x + 1.9, S:(y|x) = 13.9, r = 0.947. In the 195 cases using intraoperative PTH testing with complete results and defined clinical outcomes, the overall accuracy of the assay in predicting surgical success was 88% using the criterion of a 50% decrease at 5-10 min and 97% including the subset of patients with delayed decreases of PTH. CONCLUSIONS: The rapid PTH assay had excellent analytical performance and excellent agreement with the PTH immunoradiometric assay and predicted the success of parathyroid surgery in this large series of consecutive patients.     

不同血液净化方法对慢性肾功能衰竭维持性血液透析患者血清甲状旁腺素的影响

目的比较不同血液净化技术对慢性肾功能衰竭(肾衰)维持性血液透析患者血清甲状旁腺素(PTH)的清除效果.方法符合入选标准的90例慢性肾衰维持性血液透析患者随机分为血液吸附(AP)组、血液透析滤过(HDF)组、血液透析(HD)组3组.AP组接受血液吸附联合血液透析治疗,HDF组接受血液透析滤过1次,HD组接受血液透析治疗.用放射免疫法测定血清PTH水平;记录患者治疗前后血白蛋白、球蛋白、尿素氮、肌酐、PTH的变化,比较3组的肾小球滤过率(GFR)和透析时间.结果①AP组患者治疗后血PTH从(291.7±237.5)ng/L降至(122.2±114.5)ng/L,平均单次清除率为48.6%±55.2%,治疗前后比较有显著性差异(P<0.05);皮肤瘙痒缓解率为83.3%(10/12例).②HDF组患者治疗后血PTH从(325.9±423.1)ng/L降至(90.9±93.7)ng/L,平均单次清除率为59.5%±22.7%.治疗前后比较有显著性差异(P<0.05);皮肤瘙痒缓解率为50.0%(4/8例).③HD组患者治疗后血PTH从(297.7±211.3)ng/L降至(248.1±105.5)ng/L,平均单次清除率为13.1%±30.2%,治疗前后比较无显著性差异(P>0.05);皮肤瘙痒缓解率为14.3%(1/7例).结论①血液吸附联合血液透析治疗慢性肾衰能有效清除PTH,缓解皮肤瘙痒症状.②血液透析滤过能有效清除PTH,缓解皮肤瘙痒症状.③血液透析不能有效清除PTH,也不能有效缓解皮肤瘙痒症状.     

Value of parathyroid hormone assay for preoperative sonographically guided parathyroid aspirates for minimally invasive parathyroidectomy

PURPOSE: The key to successful parathyroid surgery is accurate preoperative tumor localization. This study investigates the use of ultrasound (US)-guided parathyroid fine needle aspiration (FNA) as a confirmatory diagnostic method in patients with hyperparathyroidism undergoing minimally invasive parathyroidectomy. METHODS: Patients were selected for minimally invasive parathyroidectomy based on the finding of a single parathyroid adenoma identified with US and/or sestamibi scans and confirmation of the suspected parathyroid lesion via FNA and parathyroid hormone (PTH) assay. The value of aspirate obtained from the thyroid gland intraoperatively served as the negative control. RESULTS: A total of 56 tissue FNAs were performed in 27 patients. US detected masses suggestive of parathyroid lesion in all 27 patients, and 31 US-guided FNAs were performed. No complications related to the procedure were noted. Intraoperatively, FNA was performed in the thyroids of 25 patients undergoing minimally invasive parathyroidectomy. Aspirates from lesions subsequently confirmed as having developed from the parathyroid gland had a mean PTH level of 4,677 +/- 123 pg/ml (range, 3,600-5,000 pg/ml), which was significantly higher than thyroid aspirates, which yielded a mean PTH level of 48 +/- 7 pg/ml (range, 5-57 pg/ml). The sensitivity of US and sestamibi scans in the detection of abnormal parathyroid glands was 88% and 77%, respectively. The sensitivity of US-guided FNA in confirming the parathyroid origin of a lesion was 100%. CONCLUSION: US-guided FNA for PTH assay can be performed safely for the confirmation of lesions identified with preoperative US for the selection of patients eligible for minimally invasive parathyroidectomy.     

Comparative analysis of serum analyte level measurements by commercial diagnostic kits from four manufacturers (Alkor-Bio,Roche, Diagnostic Products Corporation-DCP,and Bayer Corporation)

Hydrocortisone, progesterone, testosterone, triiodothyronine, thyroxine, chorionic gonadotropin, prolactin, alpha-fetoprotein, luteinizing, follicle-stimulating, and thyrotropic hormones were measured in human sera and in Lyphochek Immunoassay Plus Control reference sera (Bio-Rad Laboratories, USA) using 4 commercial kits (Alkor Bio Inc. and Roche, automated analyzer Roche Cobas Core; DPC, automated analyzer Immulite; Bayer, automated analyzer ACS:180). Coordination and correlation between these kits was observed, the coordination decreasing in the series Alkor Bio/Bayer, Alkor Bio/Roche, and Alkor Bio/DPC.     

Arginine pharmacokinetics in humans assessed with an enzymatic assay adapted to a centrifugal analyzer

Arginine is used in supra-physiological concentrations as an insulin secretagogue, in both in vitro and in vivo studies. To investigate the pharmacokinetics of arginine in humans, we have developed a rapid, automated assay of arginine in serum, based on our manual enzymatic method (Clin Chim Acta 1988, 176; 185-94). The limit of linearity of the automated assay was an arginine concentration of 3 mmol/L. Within-run CVs for Ortho control sera with added arginine were 5.5%, 0.8%, and 0.7% at concentrations of 0.16, 1.30, and 2.50 mmol/L, respectively. After 30 min of primed continuous infusions with arginine at infusion rates of 3, 9, 15, and 21 mg/kg per minute, mean (+/- SEM) arginine concentrations in serum from eight volunteers were 1.17 +/- 0.08, 3.44 +/- 0.21, 6.84 +/- 0.58, and 9.25 +/- 0.39 mmol/L, respectively, well within the range of arginine concentrations shown (in vitro) to stimulate insulin secretion. Metabolic clearance of arginine was approximately 11 mL/kg body wt per minute. For the lowest three infusion rates, the half-life (t1/2) of arginine was approximately 15 min and the volume of distribution (Vd) was approximately 290 mL/kg. At the highest infusion rate, t1/2 was significantly increased (27.3 +/- 3.1 min), owing to an increased Vd (446 +/- 83 mL/kg).     

Clinical evaluation of two novel biointact PTH(1–84) assays in hemodialysis patients

Objectives

In chronic kidney disease–mineral and bone disorder (CKD-MBD), most treatment decisions are guided by parathyroid hormone (PTH) levels. Here, we aimed at assessing the technical and clinical performance of two novel automated biointact PTH(1–84) assays, from Roche Diagnostics (Ro) and DiaSorin (DS), in hemodialysis patients.

Design and methods

We recorded demographics, dialysis treatment characteristics, pharmacotherapy for CKD-MBD and laboratory work-up. Statistical methods included Passing–Bablok, and multiple linear regression.

Results

121 patients, dialyzing on average for 3.5 years (range: 0.1–22.5), with serum phosphate 1.9 ± 0.6 mmol/L (mean ± SD), participated in the study. Median serum concentration for intact PTH was 223 ng/L (range: 5–2844), and for biointact PTH(1–84) was 136 ng/L (Ro; range: 1–1644), respectively 138 ng/L (DS; range: 4-1580). Both biointact assays were significantly correlated (r = 0.98; Ro = 0.87 × DS + 19.60). Bland–Altmann plots revealed an average bias ± 2 SD of 10 ± 27 ng/L below 200 ng/L, and − 32 ± 157 ng/L above 200 ng/L (Ro minus DS). The variably adjusted association between PTH and serum phosphate was very similar, regardless of the PTH assay, but this was not the case for PTH-derived measures (ratios biointact/intact; differences intact minus biointact). (Log)PTH concentrations as well as serum phosphate were significantly associated with serum creatinine, but only in patients with > 0 mL urine per day.

Conclusions

Results from Roche and DiaSorin biointact PTH(1–84) assays were well correlated, but showed increased deviations at higher concentrations. Biointact PTH(1–84) levels are roughly two third of intact PTH. The association between PTH and serum creatinine may depend on residual renal clearance of PTH and/or serum phosphate.     

Automated chemiluminescence-immunoassay for aldosterone during dynamic testing: comparison to radioimmunoassays with and without extraction steps

BACKGROUND: Measurements of aldosterone have become more common since the recognition that primary aldosteronism is a more frequent cause of hypertension than previously believed. Our aim was to compare concentrations reported by 4 assays for samples obtained after saline infusion during dynamic testing. METHODS: We tested 104 participants (27 with primary aldosteronism, 30 with essential hypertension, and 47 healthy controls) with the intravenous saline infusion test (2.0 L isotonic saline over 4 h), with repetitive sampling. In all blood samples, aldosterone concentration was measured by an in-house RIA after extraction and chromatography, by 2 commercially available RIAs without extraction (Aldosterone Maia, Adaltis; Active Aldosterone, Diagnostics Systems Laboratories) and by an automated CLIA (Advantage, Nichols Institute Diagnostics). RESULTS: Correlation coefficients for results of pairs of assays ranged from 0.74 to 0.98. Agreement between commercial assays and in-house RIA was best at the low to intermediate concentrations after saline infusion. Mean (SD) Adaltis and DSL RIA results were 2- to 3-times higher [healthy participants: 78 (25) ng/L and 56 (18) ng/L, respectively] than those obtained by Nichols CLIA [17 (8) ng/L] and in-house RIA [23 (18) ng/L]. Aldosterone concentrations measured by the Nichols CLIA were below the limit of detection (limit of the blank) in 27 of 47 healthy participants. CONCLUSIONS: Aldosterone concentrations reported by the Adaltis and DSL nonextraction RIAs were consistently higher than those produced by the Nichols CLIA and the in-house RIA. The convenient Nichols CLIA showed better agreement with the in-house RIA, but the concentrations in healthy participants were frequently undetectable by this method. Uncritical application of cutoff values from the literature must be avoided.     

Direct measurement of LDL-C in children: performance of two surfactant-based methods in a general pediatric population

OBJECTIVES: Several pediatric advisory groups have recommended selective screening for dyslipidemia in children. Low-density lipoprotein cholesterol (LDL-C) is measured clinically with the Friedewald calculation in fasting samples. Nonfasting measurement of LDL-C would be clinically useful in children. DESIGN AND METHODS: In the present study, we examine the performance of two surfactant-based direct LDL-C assays in paired samples, fasting and nonfasting, from 100 children. RESULTS: LDL-C in the fasting state was significantly lower with the Friedewald estimation: 2.43 +/- 0. 61 mmol/L, N-geneous (Genzyme Corp.) direct LDL-C: 2.30 +/- 0.59 mmol/L, and Roche (Roche Diagnostics) direct LDL-C: 2.32 +/- 0.57 mmol/L than with ultracentrifugation-dextran-sulfate-Mg(2+) precipitation (UC-DS): 2.47 +/- 0.64 mmol/L. Moreover, there was increased negative bias using nonfasting samples with N-geneous: 2. 25 +/- 0.56 mmol/L and Roche: 2.26 +/- 0.56 mmol/L compared with fasting UC-DS. Correlation with US-DS was highest for Friedewald (r = 0.974) and fasting N-geneous (r = 0.973), and lowest with nonfasting N-geneous (r = 0.849) and Roche in fasting (r = 0.891) and nonfasting samples (r = 0.747). The sensitivity at LDL-C concentration of 2.85 mmol/L for the two direct methods when either fasting or nonfasting samples were used, was lower than that obtained with Friedewald. CONCLUSION: Overall, these direct LDL-C assays demonstrated limited utility in screening children but may be useful in the management of lipid disorders.     

Zidovudine disposition in patients with severe renal impairment: influence of hemodialysis

Pharmacokinetics of zidovudine (azidothymidine, AZT) was investigated after oral administration (200 mg) in 25 HIV seronegative subjects: 14 patients with severe renal impairment (creatinine clearance 6 to 31 ml/min), five hemodialyzed anuric patients, and six healthy subjects. Plasma and urine concentrations of zidovudine and its glucuronidated metabolite (GAZT) were measured simultaneously by HPLC assay. In healthy subjects, GAZT concentrations were higher than those of AZT; AUC values were 23.7 +/- 1.9 and 5.2 +/- 0.6 mumol.hr/L, respectively. Formation of GAZT rate-limits its elimination: GAZT half-life (t 1/2) parallels that of AZT, which is around 1 hour. In uremic patients, AZT concentrations were moderately increased (AUC = 11.7 +/- 1.1 mumol.hr/L), whereas t 1/2 and mean residence time (MRT) remain unchanged despite the decreased renal clearance (16 +/- 2 versus 220 +/- 58 ml/min) and decreased urinary excretion (1.6 +/- 0.3 versus 8.1 +/- 1.0% of the dose). In contrast, GAZT concentrations are markedly increased (AUC = 402.9 +/- 88.6 mumol.hr/L). As a consequence of the decreased renal clearance (27 +/- 3 versus 331 +/- 42 ml/min), elimination is the rate-limiting step and t 1/2 is increased (8 +/- 2 versus 0.9 +/- 0.1 hr). Contribution of a 4-hour hemodialysis session to AZT elimination appears to be negligible, whereas elimination of GAZT is enhanced. On the sole basis of AZT pharmacokinetic data, no particular dose adjustment appears to be necessary in patients who have severe renal impairment (creatinine clearance between 10 and 30 ml/min). However, high levels of GAZT should be anticipated with the usual dosage regimen.     

Nonpeptide factor Xa inhibitors III: effects of DPC423, an orally-active pyrazole antithrombotic agent,on arterial thrombosis in rabbits

DPC423 [1-[3-(aminomethyl)phenyl]-N-[3-fluoro-2'-(methylsulfonyl)[1,1'-biphenyl]-4-yl]-3-(trifluoromethyl)-1H-pyrazole-5-carboxamide] is a synthetic, competitive, and selective inhibitor of coagulation factor Xa (fXa) (K(i): 0.15 nM in humans, 0.3 nM in rabbit). The objective of this study was to compare effects of DPC423, enoxaparin (low-molecular-weight heparin), and argatroban (thrombin inhibitor) on arterial thrombosis and hemostasis in rabbit models of electrically induced carotid artery thrombosis and cuticle bleeding, respectively. Compounds were infused i.v. continuously from 60 min before artery injury or cuticle transection to the end of experiment. Carotid blood flow was used as a marker of antithrombotic effect. Antithrombotic ED(50) values were 0.4 mg/kg/h for enoxaparin (n = 6), 0.13 mg/kg/h for argatroban (n = 6), and 0.6 mg/kg/h for DPC423 (n = 12). DPC423 at the maximum antithrombotic dose increased activated partial thromboplastin time and prothrombin time (n = 6) by 1.8 +/- 0.07- and 1.8 +/- 0.13-fold, respectively, without changes in thrombin time and ex vivo thrombin activity. The antithrombotic effect of DPC423 was significantly correlated with its ex vivo anti-fXa activity (r = 0.86). DPC423 at 1, 3, and 10 mg/kg p.o. increased carotid blood flow (percent control) at 45 min to 10 +/- 4, 24 +/- 6, and 74 +/- 7, respectively (n = 6/group). Cuticle bleeding times (percent change over control) determined at the maximum antithrombotic dose were 88 +/- 12 for argatroban, 69 +/- 13 for heparin, 4 +/- 3 for enoxaparin, 5 +/- 4 for DPC423, and -3 +/- 2 for the vehicle (n = 5-6/group), suggesting dissociation of antithrombotic and bleeding time effects for DPC423 and enoxaparin. The combination of aspirin and DPC423 at ineffective antithrombotic doses produced significant antithrombotic effect. Therefore, these results suggest that DPC423 is a clinically useful oral anticoagulant for the prevention of arterial thrombosis.     

Evaluation of the performance and clinical impact of a rapid intraoperative parathyroid hormone assay in conjunction with preoperative imaging and concise parathyroidectomy

BACKGROUND: (99m)Tc-sestamibi scans and rapid, intraoperative intact parathyroid hormone (PTH) assays allow preoperative identification of diseased glands and intraoperative confirmation of diseased gland removal, respectively. Use of these two new technologies may facilitate simpler, more concise surgery, shorter hospital stays, and decreased costs for frozen-section analysis. One major drawback to this new strategy has been the high cost of rapid point-of-care PTH assays. METHODS: We performed rapid PTH assays with the DPC Turbo PTH assay on the DPC IMMULITE automated analyzer. The number of intraoperative frozen sections, type of anesthesia, surgical approach, length of hospital stay, and pre- and postoperative calcium values were compared between a group of 49 patients undergoing parathyroidectomy where the intraoperative PTH assay was used in conjunction with preoperative imaging, and a historical control group of 55 patients before the use of these two technologies in our institution. RESULTS: Comparison of the Turbo PTH assay to the standard IMMULITE PTH assay gave the following: y = 1.08 x - 4.36 (r = 0.97; n = 48). For the 49 patients, the median turnaround time for each intraoperative PTH determination was 19 min (range, 14-40 min). The median decrease in PTH values from baseline was 88% (range, 33-99%). Thirty-seven patients required two PTH determinations, 7 required three, 4 had four, and 1 required five determinations. The average laboratory cost for the rapid intraoperative PTH assays was < $100 per patient (range, $55 to $113). Compared with the control group, the experimental group had significantly fewer frozen sections (1.4 vs 2.5; P < 0.0001), shorter hospital stays (17 discharged on the day of surgery vs none discharged on the day of surgery; P < 0.0001), greater use of local anesthesia (33% vs 0%; P < 0.001), and more unilateral, rather than bilateral neck explorations (65% vs 0%; P < 0.001). CONCLUSIONS: The combination of intraoperative Turbo PTH assay and preoperative (99m)Tc-sestamibi scans can lead to significant decreases in laboratory and surgical pathology costs, hospital stays, and exposure to general anesthesia by facilitating concise parathyroidectomy surgery.     

Quantitative automated human chorionic gonadotropin measurement in urine using the Modular Analytics E170 module (Roche).

Ongoing demands on laboratory performance require optimization of processes. An obvious way to achieve this is to reduce manual labor in favor of automated methods. We describe the validation of an automated quantitative urine human chorionic gonadotropin (hCG) analysis on the Roche Modular E170 analyzer to replace the manual qualitative pregnancy test in urine. At urine hCG concentrations of 476, 45 and 11 U/L, we found inter-assay variation of 4.3%, 4.3% and 6.8% and average intra-assay variation of 3.0%, 2.6% and 3.0%, respectively. The analytical detection limit was 0.7 U/L. We did not detect any loss (due to degradation or adsorption) during a storage period of 5 days at 4 degrees C or at -20 degrees C. Recoveries of hCG in urine of a pregnant woman diluted with urine of a pre-menopausal non-pregnant woman (concentration range between 6 and 800 mU/L) were between 93% and 112% (y=0.997x-3.843, r 2 =0.999). Diluting a serum sample (hCG 42,000 U/L) with urine (negative for hCG) up to 8000-fold yielded a completely linear hCG response, indicating that the assay was not affected by the urine matrix. In a correlation study with 60 urine samples (of which 10 were of male origin), we did not find any discrepancies between results for the manual pregnancy test and the hCG test on the Roche Modular E170 (using a cutoff value of 50 U/L).     

Technical and clinical characterization of the Bio-PTH (1-84) immunochemiluminometric assay and comparison with a second-generation assay for parathyroid hormone

BACKGROUND: The Bio-Intact parathyroid hormone (1-84) assay (Bio-PTH), a newly developed two-site immunochemiluminometric assay, measures exclusively PTH (1-84) in contrast to second-generation "intact PTH" (I-PTH) assays. We investigated the technical performance and clinical significance of this new assay. METHODS: PTH was measured simultaneously by the Bio-PTH assay and Allegro intact PTH IRMA in sera from Japanese patients with calcium disorders. RESULTS: Measured Bio-PTH in serum was unaffected by six freeze-thaw cycles and was stable at 4 degrees C for 7 days and during storage at -20 or -80 degrees C over 28 days. The calibration curve was linear to 1800 ng/L. The detection limit was 3.9 ng/L. The intra- and interassay imprecision was <2.8% and 3.5%, respectively, for analyte concentrations spanning the range of the calibration curve. Bio-PTH was unaffected by a 1000-fold excess of PTH (7-84), although I-PTH reacted equally with PTH (7-84) and PTH (1-84). Bio-PTH was correlated with I-PTH in healthy individuals (r = 0.953; P <0.0001; n = 26) and in the full population without renal dysfunction (r = 0.994; P <0.0001; n = 62). In 72 volunteers, mean (SD) Bio-PTH was 22.2 (7.1) ng/L, or 62% of the mean I-PTH [36.1 (22.3) ng/L]. This ratio was 51% in hemodialysis patients (n = 177). Mean Bio-PTH was high in patients with primary hyperparathyroidism [121 (85) ng/L; n = 18] and hemodialysis patients [102 (104) ng/L; n = 177], low in idiopathic hypoparathyroidism [5.5 (2.8) ng/L; n = 4], and within 2 SD of the mean for healthy controls in Paget disease of the bone [34 (15) ng/L; n = 9] and bone metastasis [24 (12) ng/L; n = 8]. CONCLUSION: The Bio-PTH assay is sensitive and precise and produces expected results for patients with the studied disorders of calcium metabolism.     

Evidence for Skeletal Resistance to Parathyroid Hormone in Magnesium Deficiency: STUDIES IN ISOLATED PERFUSED BONE

Hypocalcemia during magnesium (Mg) depletion has been well described, but the precise mechanism(s) responsible for its occurrence is not yet fully understood. The hypocalcemia has been ascribed to decreased parathyroid hormone (PTH) secretion as well as skeletal resistance to PTH. Whereas the former is well established, controversy exists as to whether or not Mg depletion results in skeletal resistance to PTH. These studies examine the skeletal response to PTH in normal dogs and dogs fed a Mg-free diet for 4-6 mo. Isolated tibia from normal (serum Mg 1.83+/-0.1 mg/100 ml) and experimental dogs (serum Mg 1.34+/-0.15 mg/100 ml) were perfused with Krebs-Henseleit buffer during a constant infusion of 3 ng/ml of synthetic bovine PTH 1-34 (syn b-PTH 1-34). The arteriovenous (A-V) difference for immunoreactive PTH (iPTH) across seven normal bones was 37.5+/-3%. In contrast, the A-V difference for iPTH was markedly depressed to 10.1+/-1% across seven bones from Mg-depleted dogs. These findings correlated well with a biological effect (cyclic AMP [cAMP] production) of syn b-PTH 1-34 on bone. In control bones, cAMP production rose from a basal level of 5.8+/-0.2 to 17.5+/-0.7 pmol/min after syn b-PTH 1-34 infusion. In experimental bones, basal cAMP production was significantly lower than in controls, 4.5+/-0.1 pmol/min, and increased to only 7.1+/-0.4 pmol/min after syn b-PTH 1-34 infusion. Even when PTH concentrations were increased to 20 ng/ml, cAMP production by experimental bones was lower than in control bones perfused with 3 ng/ml. Histological examination of bones from Mg-deficient dogs showed a picture compatible with skeletal inactivity. These studies demonstrate decreased uptake of iPTH and diminished cAMP production by bone, which indicates skeletal resistance to PTH in chronic Mg deficiency.     

Kinetics of intravenous and intramuscular morphine

The disposition of parenteral morphine was assessed in two pharmacokinetic studies. In Study 1, 10 mg of morphine sulfate was administered by intravenous (IV) infusion, intramuscular (IM) injection, or both, to 8 healthy young adult male volunteers. Plasma morphine concentrations were determined by radioimmunoassay in multiple blood samples drawn after each dose. Mean (+/-SE) kinetic parameters following IV morphine were: volume of distribution (Vd), 3.2 (+/- 0.3) L/kg; elimination half-life (t1/2beta), 2.9 (+/- 0.5) hr; clearance, 14.7 (+/- 0.9) ml/min/kg; extraction ratio, 0.70 (+/- 0.04). After IM morphine, peak plasma levels ranged from 51 to 62 ng/ml and were reached within 20 min of injection. The absorption half-life averaged 7.7 (+/- 1.6) min. Systemic availability was 100% complete. In study 2, 4 elderly male patients (61 to 80 yr of age) received 45 to 80 mg of morphine sulfate IV prior to operative repair of an abdominal aortic aneurysm. Morphine pharmacokinetics were determined as described above. Kinetic variables were Vd, 4.7 (+/- 0.2) L/kg; t1/2beta, 4.5 (+/- 0.3) hr; clearance, 12.4 (+/- 1.2) ml/min/kg; extraction ratio, 0.59 (+/- 0.05). Both studies demonstrate that morphine distribution is rapid and extensive and its t1/2beta relatively short. IM morphine is rapidly and completely absorbed.